1. Field of the Invention
The present invention relates to an electrostatic copying machine having a photoreceptor of an endless belt type and, more particularly, to an arrangement thereof for the easy exchange of the photoreceptor belt.
2. Description of the Prior Art
According to the prior art copying machine of the above described type, such as disclosed in U.S. Pat. No. 4,332,458, it is a time consuming task to exchange the endless belt. According to U.S. Pat. No. 4,332,458, the photoreceptor belt is mounted extendingly on the large diameter roller and the small diameter roller in a teardrop cross section.
When it is necessary to exchange the photoreceptor belt, the operator first must bring the copying machine to an open space. Then, he draws out the rollers and photoreceptor belt together with the associated parts in a direction perpendicular to the axis of the rollers from the housing of the copying machine in a manner similar to a match box. If there is a cover provided around the photoreceptor belt to protect it form the external lights, the operator must open the cover. Then, he releases the tension on the photoreceptor belt by narrowing the distance between the large and small rollers. Since the rollers are supported in cantilever fashion, the photorecepter belt is removed in the axial direction of rollers.
When a new photoreceptor belt is mounted, the rollers are stretched out again to provide tension to the new photoreceptor belt. Then, the light protection cover is closed and, thereafter, the drawer is pushed back into the housing.
The prior art copying machine has a problem in the quality of the reproduced image on a copy paper, and also a problem in difficulty in exchanging the photoreceptor belt.
Specifically, since the rollers are supported in cantilever fashion, they are susceptible to external forces applied thereto in the direction perpendicular to the axis, particularly at the free ends thereof. Therefore, after a long period of use, the rollers may not be maintained in the required positions, resulting in unevn lighting of the original image on the photoreceptor surface or in deflection of the reproduced image. Although this may be improved by forming the cantilever arrangement with a stiff material, the copy machine becomes bulky and expensive.
Furthermore, when the new photoreceptor belt is mounted, one may set up the copying machine in a condition ready for taking copies with the belt not completely mounted. In such a case, a part of the image may not be reproduced, or the copying operation may not start in the case when there is a detector that detects the condition of the mounted photoreceptor belt.
Moreover, since there are a number of steps that have to be carried out to complete the photoreceptor belt exchange, one may forget to do some of the steps. For example, one may forget to stretch out the rollers after the new photoreceptor belt is mounted to provide a tension to the belt, or one may forget to close the light protection cover. In such a case, parts, such as cover and belt, may be damaged, and/or the reproduced image will be in a very poor condition.